Field of the Invention
This disclosure is directed to medical implant devices and the manufacture thereof.
Description of Related Art
Medical devices capable of being implanted in a body are known as medical implant devices, implantable medical devices, medical implants, etc. Cases or housings for such devices can be constructed from titanium and titanium alloys. Pure titanium, for example Grade 1 titanium, is generally easier to cold form than titanium alloys, and has a lower electrical resistivity than titanium alloys. At room temperature, Grade 1 titanium has an elongation of about 30%, whereas a titanium alloy might only have 10% to 15% elongation, making the titanium alloy more difficult to cold form. With titanium alloys, excessive spring-back and cracking can be exhibited in areas of large deformation when cold forming these materials into shapes suitable for compact implantable medical devices. This can lead to design compromises when designing a titanium alloy housing for an implantable medical device. Such design compromises can include larger radii for curves on the housing, more generous tolerances, etc. Hot stamping the titanium alloy might be employed to slightly increase the elongation percent, but the design freedom for the housing will still be limited. Moreover, both hot and cold stamping typically require a post vacuum annealing procedure in order to reduce residual stress and remove surface formation of brittle alpha case, caused by processing in ambient air, that can lead to microcracking and reduced fatigue life.